Water reclamation can cause significantly more nitrous oxide (N20) emissions than traditional water treatment, according to an article in the September Journal of Environmental Quality.
The researchers, led by Amy Townsend-Small of the University of Cincinnati, measured N20 concentrations and fluxes from several wastewater treatment processes in urban southern California.
The authors found that removal of nitrogen during water reclamation, through microbial nitification and denitrification, may lead to in situ N20 emission rates three or more times greater than traditional treatment processes. In the reclamation processes studied, N20 production was 1.2 percent of total nitrogen removed, compared to 0.4 percent for traditional treatment.
Nitrous oxide is a long-lived and potent greenhouse gas, the authors said, and centralized water reclamation plants are potentially a large source of N20 in urban areas of developed countries. But despite the problems with water reclamation, it is still a powerful tool for urban areas, Townsend-Small told Science Daily.
“Advanced methods in wastewater treatment supplement fresh water supplies in areas where fresh water is scarce,” Townsend-Small said. “Climate change, caused at least in part by human-made greenhouse gas emissions, is expected to exacerbate freshwater scarcity in many of these areas, including the United States southwest.”
Picture credit: Renee Silverman